This application claims priority from European Patent Application No: 04 029 928.1 filed Dec. 17, 2004, herein incorporated by reference in its entirety.
The invention relates to an arrangement for coating a substrate.
Recent developments in the production of flat screens for computers or television sets are oriented toward the so-called organic light-emitting diodes (OLEDs). The production of OLEDs can take place by means of OVPD technology (OVPD—Organic Vapor Phase Deposition, U.S. Pat. No. 5,554,220), in which a carrier gas stream at very low pressure in a heated reactor takes up organic materials and deposits these as thin layers on a substrate.
In another method for coating a substrate with a thin organic layer, a substrate holder with heating means is provided, which holds on its lower surface a substrate, for example glass (EP 0 962 260 A1=U.S. Pat. No. 6,101,316). Beneath this substrate are provided two evaporation sources, which vaporize organic material, which is deposited on the substrate if a shutter disposed between the substrate and the vaporizer is opened.
Also known is an electrically actuated valve for glass apparatus, which can be opened and closed by means of an electric motor (DE 201 15 333 U1). The valve body is herein implemented as a cylinder.
Further is known an all-metal valve with a slidable and a resting sealing partner, of which the one sealing partner is implemented in the form of a plate (DE 30 15 487 A1). This valve comprises an additional sealing partner, which becomes operational if the plate-shaped sealing partner is defective.
In another known valve the valve body is implemented as a ball, this ball being capable of closing a cylindrical tube (Japan 2000120551 A).
A ball-shaped body also comprises a valve, which can be utilized in the environment of aggressive materials (U.S. Pat. No. 3,887,162).
A valve is furthermore known, which comprises a ball-shaped closure body (U.S. Pat. No. 4,195,666). This valve is utilized for controlling highly corrosive fluids. It has the capacity of blocking fluids in two different positions.
A servo-controlled valve for mixing two fluids in a specific ratio is disclosed in U.S. Pat. No. 3,561,484. This valve also comprises a ball-shaped closure body.
An evaporation apparatus with a source for vaporized organic material comprising an on-off valve is known from U.S. Pat. No. 6,101,316. An evacuation device is herein connected with a container containing organic material, the evacuation device evacuating the container when the valve is closed.
Arrangements for the evaporation of OLED materials are also disclosed in EP 1 357 200 A1 and EP 1 401 036 A2.
Lastly, an arrangement for coating an areal substrate is known, which comprises a stationary evaporation source for the vaporization of materials, with which the substrate is to be coated (DE 102 24 908 A1). This arrangement comprises a driving means which moves the areal substrate relative to the evaporation source. It comprises, in addition, a first distributor arrangement, which linearly distributes the vapor emitted by the evaporation source, as well as a second distributor arrangement, which is disposed at its one end at least in the proximity of the evaporation source and which terminates with its other end in the first distributor arrangement. This known arrangement is layed out for continuous evaporation, which means, a coating process once started is to be carried out over several hours or days. Due to good insulation and a large thermal mass, the control behavior of the evaporation source is very slow. From the time the heating means of the evaporation source is switched on, it takes more than one hour before a desired rate is reached, and the switching-off of the evaporation source—from the time the heating means is switched off until the evaporation rate is zero—takes a correspondingly long time.
During this time the very expensive material is vaporized from the evaporation source without being utilized for coatings. If between the substrate and the evaporation source a shutter is provided, the material becomes deposited on this shutter. A short-term interruption of the evaporation of a few minutes is not possible.
The invention therefore addresses the problem of interrupting the material flow from the evaporation source to the substrate and simultaneously saving evaporation material.
The problem is resolved according to the present invention, which relates in part to an arrangement for coating a substrate, which comprises an evaporation source and a vapor barrier between the evaporation source and the substrate. The vapor barrier is maintained at a temperature which is at least equal to or greater than the vaporization temperature of the material to be vaporized.
The vapor barrier is implemented as a quartz valve, which includes a ball-shaped closure part connected with a movable rod. In a first position this ball-shaped closure part closes a vapor conducting tube connected with the evaporation source, and, in a second position, the ball-shaped closure part abuts a spherical calotte which seals off a quartz tube.
The advantage obtained with the invention resides in particular therein that the evaporation is interrupted and therewith no deposition of the material onto structural parts occurs, which are not the substrate. Thus, on the one hand, with the valve closed the substrate is no longer coated and, on the other hand, evaporation material is no longer consumed. Through the particular implementation of the vapor barrier as a special valve it is ensured that in the open position of the valve, on the one hand, the tube cross section is made available for the vapor flow and, on the other hand, the rearward space of the valve is sealed off against the penetration of the vapor into the valve guide so that it does not become stuck.
A special implementation of the valve is described herein.
An embodiment example of the invention is shown in the drawing and will be described in the following in further detail.